In India there are giant catfish in some of the rivers that have supposedly developed a taste for human flesh (people are often partly cremated and dumped in the headwaters of the Ganges, which supposedly releases them from the cycle of death and rebirth). And those catfish are rumoured to have been responsible for eating small children who were swimming in the river.
I saw this on the show "River Monsters" which I always assumed was a little bit embellished.